From 5afbd223e60a130f66bddf7598165ebe2b51f8db Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 30 Aug 2016 00:35:07 -0400 Subject: KEYS: Fix ASN.1 indefinite length object parsing [ Upstream commit 23c8a812dc3c621009e4f0e5342aa4e2ede1ceaa ] This fixes CVE-2016-0758. In the ASN.1 decoder, when the length field of an ASN.1 value is extracted, it isn't validated against the remaining amount of data before being added to the cursor. With a sufficiently large size indicated, the check: datalen - dp < 2 may then fail due to integer overflow. Fix this by checking the length indicated against the amount of remaining data in both places a definite length is determined. Whilst we're at it, make the following changes: (1) Check the maximum size of extended length does not exceed the capacity of the variable it's being stored in (len) rather than the type that variable is assumed to be (size_t). (2) Compare the EOC tag to the symbolic constant ASN1_EOC rather than the integer 0. (3) To reduce confusion, move the initialisation of len outside of: for (len = 0; n > 0; n--) { since it doesn't have anything to do with the loop counter n. Signed-off-by: David Howells Reviewed-by: Mimi Zohar Acked-by: David Woodhouse Acked-by: Peter Jones Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- lib/asn1_decoder.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) (limited to 'lib') diff --git a/lib/asn1_decoder.c b/lib/asn1_decoder.c index 2b3f46c049d4..554522934c44 100644 --- a/lib/asn1_decoder.c +++ b/lib/asn1_decoder.c @@ -74,7 +74,7 @@ next_tag: /* Extract a tag from the data */ tag = data[dp++]; - if (tag == 0) { + if (tag == ASN1_EOC) { /* It appears to be an EOC. */ if (data[dp++] != 0) goto invalid_eoc; @@ -96,10 +96,8 @@ next_tag: /* Extract the length */ len = data[dp++]; - if (len <= 0x7f) { - dp += len; - goto next_tag; - } + if (len <= 0x7f) + goto check_length; if (unlikely(len == ASN1_INDEFINITE_LENGTH)) { /* Indefinite length */ @@ -110,14 +108,18 @@ next_tag: } n = len - 0x80; - if (unlikely(n > sizeof(size_t) - 1)) + if (unlikely(n > sizeof(len) - 1)) goto length_too_long; if (unlikely(n > datalen - dp)) goto data_overrun_error; - for (len = 0; n > 0; n--) { + len = 0; + for (; n > 0; n--) { len <<= 8; len |= data[dp++]; } +check_length: + if (len > datalen - dp) + goto data_overrun_error; dp += len; goto next_tag; -- cgit v1.2.3 From 11c27e850d90372d79c1337be299923b5fb353e8 Mon Sep 17 00:00:00 2001 From: Nicolai Stange Date: Tue, 22 Mar 2016 13:12:35 +0100 Subject: lib/mpi: mpi_write_sgl(): fix skipping of leading zero limbs commit f2d1362ff7d266b3d2b1c764d6c2ef4a3b457f23 upstream. Currently, if the number of leading zeros is greater than fits into a complete limb, mpi_write_sgl() skips them by iterating over them limb-wise. However, it fails to adjust its internal leading zeros tracking variable, lzeros, accordingly: it does a p -= sizeof(alimb); continue; which should really have been a lzeros -= sizeof(alimb); continue; Since lzeros never decreases if its initial value >= sizeof(alimb), nothing gets copied by mpi_write_sgl() in that case. Instead of skipping the high order zero limbs within the loop as shown above, fix the issue by adjusting the copying loop's bounds. Fixes: 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") Signed-off-by: Nicolai Stange Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- lib/mpi/mpicoder.c | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) (limited to 'lib') diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c index e00ff00e861c..e37dbf53e226 100644 --- a/lib/mpi/mpicoder.c +++ b/lib/mpi/mpicoder.c @@ -367,7 +367,9 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes, buf_len = sgl->length; p2 = sg_virt(sgl); - for (i = a->nlimbs - 1; i >= 0; i--) { + for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB, + lzeros %= BYTES_PER_MPI_LIMB; + i >= 0; i--) { alimb = a->d[i]; p = (u8 *)&alimb2; #if BYTES_PER_MPI_LIMB == 4 @@ -388,17 +390,12 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes, #error please implement for this limb size. #endif if (lzeros > 0) { - if (lzeros >= sizeof(alimb)) { - p -= sizeof(alimb); - continue; - } else { - mpi_limb_t *limb1 = (void *)p - sizeof(alimb); - mpi_limb_t *limb2 = (void *)p - sizeof(alimb) - + lzeros; - *limb1 = *limb2; - p -= lzeros; - y = lzeros; - } + mpi_limb_t *limb1 = (void *)p - sizeof(alimb); + mpi_limb_t *limb2 = (void *)p - sizeof(alimb) + + lzeros; + *limb1 = *limb2; + p -= lzeros; + y = lzeros; lzeros -= sizeof(alimb); } -- cgit v1.2.3